TOKYO The company that runs a Japanese nuclear power plant destroyed by a tsunami two years ago said on Tuesday it was losing faith in temporary storage pits for radioactive water - but it doesn't have anywhere else to put it.

Tokyo Electric Power Co (Tepco) said it had found a new leak at one of the pits at the Fukushima Daiichi plant. Three out of seven storage pits are now leaking, compounding clean-up difficulties after the world's worst nuclear crisis in 25 years.

"We cannot deny the fact that our faith in the underwater tanks is being lost," Tepco general manager Masayuki Ono told a hastily arranged news conference.

"We can't move all the contaminated water to above ground (tanks) if we opt not to use the underground reservoirs," Ono said. "There isn't enough capacity and we need to use what is available."

A tsunami crashed into the power plant north of Tokyo on March 11, 2011, causing fuel-rod meltdowns at three reactors, radioactive contamination of air, sea and food and triggering the evacuation of 160,000 people.

The fresh leak was found in the No. 1 storage pool where contaminated water from the leaking No. 2 pit was being transferred. Tepco has halted the transfer of the contaminated water.

Ono said on Monday Tepco did not have enough tank space should it need to move the water out of the storage pits, which were dug into higher ground away from the damaged reactors and lined with waterproof material. The company has stepped up construction of the sturdier tanks, he said.

Tepco said over the weekend about 120,000 litres (32,000 gallons) of contaminated water leaked from the No. 2 and 3 pits. The plant's cooling system has also broken down twice in recent weeks.

The government instructed Tepco to carry out a "fundamental" review of the problems at the plant, Chief Cabinet Secretary Yoshihide Suga told reporters on Monday.

Tepco's president, Naomi Hirose, was also summoned to the Industry Ministry to explain the leaks and got a public dressing down from the minister, Toshimitsu Motegi.

Immediately after the explosions at the plant, Tepco released some radioactive water into the sea, prompting protests from neighbouring countries. Many nations put restrictions on imports of Japanese food after the disaster.

It was the worst nuclear accident since the Chernobyl disaster in 1986.

Last month, a senior Tepco executive said the company was struggling to stop groundwater flooding into the damaged reactor buildings and it may take as long as four years to fix the problem.